The aim of this research is to investigate the developing axonal connections between the orbitofrontal cortex and basal ganglia and thalamus in the neonatal dog. Both lesion (Fink-Heimer and Nauta-Laidlaw) and injection H3-leucine and horseradish peroxidase) methods will be used to determine the spatial and temporal development of the axonal projections. Golgi impregnation of neurons in the cortex, caudate nucleus, and thalamus will also be done to determine the degree of development of postsynaptic elements and their relationship to developing terminal fields. BIBLIOGRAPHIC REFERENCES: Thanaka, D. and Goldman, P.S. Silver degeneration and autoradiographic evidence for a projection from the principal sulcus to the septum in the rehesus monkey, Brain Research, 103:535-540, 1976.